Ground Strap Issue
10-05-2009, 11:44 AM
#16
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10-05-2009, 12:06 PM
#17
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Similar issue and similar RL Rx. I found this thread from stylemobile and bought a replacement. Started ever since: https://rennlist.com/forums/928-foru...und-cable.html
10-05-2009, 02:25 PM
#18
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I'm a chem e, we don't usually do electrical, so I don't know how to test it. Gotta be a way, maybe heat rise with measured current. When the car finally stopped working had 12.86 volts across the battery and less than 4 volts if I moved the negative voltmeter lead to the shock tower. The previous day, as the car sat dead, I had no more than 8.3 volts anywhere else in the car, including the jump post in the front.
The good thing is this one place where you can throw a part at the car and test it inexpensively and with little time impact. I changed the cable and it worked, then a few days later found the corrosion.
The good thing is this one place where you can throw a part at the car and test it inexpensively and with little time impact. I changed the cable and it worked, then a few days later found the corrosion.
10-05-2009, 03:00 PM
#19
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If you connect one lead of a voltmeter to the battery negative post - not the clamp or cable, but the post - and the other lead to clean, bright bare metal on the chassis at the ground strap connection, there should be very close to zero volts on the meter, even when you have an assistant hit the starter. Any significant voltage reading indicates a problem.
10-05-2009, 04:46 PM
#21
Electron Wrangler
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But the problem with this is that the failure seems to be intermittent - I don't quite understand the mechanism - but multiple anecdotal info says a strap can be basically virtually open circuit and then you wiggle it a bit and it can sustain starting currents - till you wiggle it a bit more..
When it goes full time high resistance its easy to track down - car won't start - high voltage across ground strap - before that - can be very hard to diagnose.
The critical things are you do need high current conditions and you may need physical manipulation also..
The other way to test this is on a carbon pile load tester with the battery (@good battery shop) - eg test from battery+ post to ground strap end - see what happens to voltage across the ground strap when loading with high current drain conditions and flexing the strap (bit easier steady state conditions than duuring starting).
Alan
When it goes full time high resistance its easy to track down - car won't start - high voltage across ground strap - before that - can be very hard to diagnose.
The critical things are you do need high current conditions and you may need physical manipulation also..
The other way to test this is on a carbon pile load tester with the battery (@good battery shop) - eg test from battery+ post to ground strap end - see what happens to voltage across the ground strap when loading with high current drain conditions and flexing the strap (bit easier steady state conditions than duuring starting).
Alan
10-05-2009, 08:24 PM
#22
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I have several, new braided ground straps that are not sheathed in the plastic. (Is there really a legitimate reason for the sheathing anyway? The cable passes over the same parts of the body that the end ultimately connects to, no?) Anyway, If you could use one, I could check on the length to make sure it fits your model and get back to you. You would need to do the same. I'll sell cheap.
10-06-2009, 02:04 AM
#23
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I think its partly physical protection (the individual braided wires are not very robust) and partly to keep out water, dirt & all that free flowing oxygen. If you add a battery switch at the ground point the sheathing serves a useful electrical purpose too.
Alan
Alan
10-06-2009, 02:48 AM
#24
Rennlist Member
I agree that any fix to that should be considered temporary at best, even soldering.
A load tester as Alan describes is the best way to check it. I picked up a HF load tester like the one below back when they were painted blue, and cost about $50:
(Click image to go to product page)
Using one of these you can easily put 500 amps through that cable and see if it holds the magic smoke in or not!
Just watch it carefully to make sure you don't damage anything nearby. In fact you could probably detect a bad cable by checking the voltage at both ends of the cable and putting 100 amps or less through it. A load tester of this quality probably wouldn't hold up long in a shop environment but IMHO it's fine for occasional, casual use.
One additional tip: Any carbon pile device like this is probably going to let off some smoke from inside the case the first time you use it. Don't worry, it's normal.
A load tester as Alan describes is the best way to check it. I picked up a HF load tester like the one below back when they were painted blue, and cost about $50:
(Click image to go to product page)
Using one of these you can easily put 500 amps through that cable and see if it holds the magic smoke in or not!
Just watch it carefully to make sure you don't damage anything nearby. In fact you could probably detect a bad cable by checking the voltage at both ends of the cable and putting 100 amps or less through it. A load tester of this quality probably wouldn't hold up long in a shop environment but IMHO it's fine for occasional, casual use.One additional tip: Any carbon pile device like this is probably going to let off some smoke from inside the case the first time you use it. Don't worry, it's normal.
10-21-2009, 10:12 AM
#25
Rennlist Member
My car was cutting out intermittently.
Usually, tach would drop to zero, indicating a stalled car, which would then restart immediately.
Would do this at highway speed.
Worse under load or so it seemed.
Sometimes associated with hitting a bump, often not.
I "made up" all kinds of data and cause/effects. Most with a data set of 1 or 2. Thought I'd fixed it a dozen times. Baffled me.
The original flat, plastic coated ground strap failed. It failed intermittently, then terminally (so-to speak).
Today at the FRENZY 13 event, a couple of us disected the failed cable.
Despite a very good outward appearance, we found the failure (Bad localized corrosion) buried under the plastic sheathing near the end that bolts to the car body with the T-handled nut.
Jadz928 took pictures of it and will likely post them.
ALL y'all need to keep this failure in-mind. It might happen to your car. Probably sat for a long time with that area wet occasionally.
Usually, tach would drop to zero, indicating a stalled car, which would then restart immediately.
Would do this at highway speed.
Worse under load or so it seemed.
Sometimes associated with hitting a bump, often not.
I "made up" all kinds of data and cause/effects. Most with a data set of 1 or 2. Thought I'd fixed it a dozen times. Baffled me.
The original flat, plastic coated ground strap failed. It failed intermittently, then terminally (so-to speak).
Today at the FRENZY 13 event, a couple of us disected the failed cable.
Despite a very good outward appearance, we found the failure (Bad localized corrosion) buried under the plastic sheathing near the end that bolts to the car body with the T-handled nut.
Jadz928 took pictures of it and will likely post them.
ALL y'all need to keep this failure in-mind. It might happen to your car. Probably sat for a long time with that area wet occasionally.
